Have Jeep Questions? Ask a Jeep Repair Expert for Answers
Hello, My name is***** am a Chrysler Master Technician.
Sounds as if you may have a bad crankshaft position sensor. Is the check engine light on when it is running? Please be very careful using starting fluid in a gasoline engine, it can cause detonation and ruin your engine.
We will have to do some tests to see what is causing it not to start on its own.
First test i would like you to try is to go into the fuse block under the hood, and look for the ASD Relay. Swap that one with the horn relay, and attempt to start the vehicle.
Ok, lets try looking at the fuel side. Swap the horn relay and the fuel pump relay, see if the vehicle will start. This is a odd issue, so bear with me, we have to check the simple stuff first.
If you swap that relay and it doesnt start, we need to check the fuel pump module. You should hear the fuel pump actuate when you turn the key to the on position. should sound like a "whir" coming from the back of the vehicle.
I understand it runs on starting fluid, but i am thinking maybe it is drawing fuel on its own after it gets started. Have you driven the vehicle after it was started with starting fluid?
Also make sure you have checked all fuses in the fuse block under the hood. You will need a test light to verify. If those are all good, we need to check and see if we have power at the fuel pump module connector. Key on, probe the connector with the test light and see if you have power.
Ok give me one min.
Be advised, you have a open recall on your vehicle.
The skim seems to be working because it will let you spin the starter over, and it will run without killing the engine after 2 seconds.
We need to check and make sure the pcm is getting the ignition feed signal
We need to check pin number 22 with a test light, see if it lights up with the key on.
Disconnect the black connector (c1) and check the pin in relation to the diagram.
Ok, that means the pcm is getting the proper feed it needs. This one is stumping me, lets try one more thing before I opt out and let another expert try to help you.
Since you are saying it starts and runs fine on starting fluid, it is getting fuel and spark. But seems something is messing with the staring injector pulse width maybe. The pcm will look at the MAP sensor as the primary input for the starting equation (speed density), it could be that the map is sending a scewed signal. Try disconnecting the map sensor and see if it will start in default.
here is the location of the map sensor on the throttle body
Ok bud, i will opt out and see if someone else can help you. Have a good day!
Can you tell me if you have power to one of the wires at any fuel injector with key ON? thanks.
So when cranking does it hit at all and try to start? and no power to any fuel injector with key ON is a problem, but I'm wondering since you have power in START position if indeed it tries to fire up and run and then dies as soon as you turn the key back to the ON position.
Is this regular cherokee or grand cherokee? and does it have a 4.0 L straight 6 cylinder in it? thank you.
Here is the diagram of how the injectors get power, the ASD relay powers them up with key ON. The ECM (engine computer) grounds the ASD relay with the key on, Check all those fuses up top in this diagram, make sure they all have power to them and are good, and pull the ASD relay out and see if you have 2 pins in the ASD relay socket HOT with the key ON. the BLUE/YELLOW wire running to the ASD relay grounds the relay and it's ground comes from pin 3 and the ECM.
So there is only one hot pin with 12 volts with the key ON at the ASD relay socket? correct?
Alright, that's correct. and with the key ON, per the diagram, the ASD relay powers up fuse 18 and fuse 21. So check those two fuses with key ON and they both should have power. fuse 18 and 21 both are 15 amp fuses.
but you have no 12 volts at the fuel injector when the key is in START position still correct?
Alright, let me opt out so another expert can assist. I can't be online tom. and I don't want you to wait, I will check back later and see what progress is made. thank you.